With the development of information society in recent years, the amount of data is expected to increase greatly. To respond to the expected increase in the amount of data, it is necessary to install many high-performance servers and other electronic devices. Generally, high-performance electronic devices consume a large amount of electric power. And most of the electric power consumption of the electronic devices is converted into heat. Therefore, installing high-performance electronic devices cause ambient temperature rising due to their exhaust heat consequently. Particularly, in data centers having many electronic devices such as servers, the electronic devices emit a large amount of heat. In such a case, the electronic devices need to be cooled to maintain their functions, thus the air conditioning system requires a large amount of electric power. Because of that situation, there is a demand for a method of reducing load on the air conditioning of electronic devices.
As a technique to meet such a demand, there has been devised a method of circulating refrigerant without using a pump by utilizing phase changes of the refrigerant. This technique does not use any power for circulating the refrigerant and is very economical. In addition, by using an insulating refrigerant, short circuits are prevented even when there is a refrigerant leak. Thus, the technique of utilizing phase changes of the refrigerant is very effective for removing heat from servers and other electronic devices in data centers where these devices need to be working constantly.
Such electronic devices as described above are usually disposed in multiple tiers in a rack when used. In such a case, heat receivers for absorbing heat from the electronic devices are preferably disposed in multiple tiers corresponding to the tiers of electronic devices for higher efficiency.
A technique for refrigerant supply device for supplying refrigerant evenly among heat receivers disposed in multiple tiers as described above by utilizing force of gravity is disclosed in, for example, PTL 1. This technique employs a liquid distribution mechanism between liquid conduits for supplying liquid phase refrigerant and the heat exchanger. The liquid distribution mechanism is in a shape of container, and a branch conduit through which the refrigerant flows to lower tiers is connected to the liquid distribution mechanism at the same height as the predetermined level of liquid surface of the heat exchanger. When the refrigerant exceeds the predetermined level of liquid surface, the refrigerant overflows to the branch tube and flows down to the liquid distribution mechanism on a lower tier.
PTL 1 and PTL 2 disclose a configuration in which the liquid distribution mechanism is provided with a float and a valve that moves up and down with the float. In this configuration, when the refrigerant surface goes up to a predetermined level, the valve closes and subsequently the refrigerant flows down to the liquid distribution mechanism on a lower tier. PTL 3 also discloses a related technique.